The United States and China openly clashed Wednesday over the pro-democracy protests sweeping Hong Kong, with Beijing angrily warning Washington to back off and saying it would not tolerate “illegal acts.”

“The Chinese government has very firmly and clearly stated its position. Hong Kong affairs are China’s internal affairs,” Foreign Minister Wang Yi told US Secretary of State John Kerry, who was standing next to him, just before they went into talks at the State Department.

“All countries should respect China’s sovereignty and this is a basic principle of governing international relations,” Wang said sternly.

“I believe for any country, for any society, no one would allow those illegal acts that violate public order. That’s the situation in the United States and that’s the same situation in Hong Kong.”

Washington has always walked a delicate tightrope in its relations with China, eager to improve trade and economic ties with the world’s second largest economy while also pressing for greater human rights.

Amid a tense standoff on the streets of Hong Kong, a Chinese territory, Kerry renewed US calls for restraint by the city’s police.

The Basic Law is the mini-constitution of Hong Kong, where Beijing is grappling with one of the biggest challenges to its rule of the territory.

“We believe an open society with the highest possible degree of autonomy and governed by rule of law is essential for Hong Kong’s stability and prosperity,” Kerry added.

“And we have high hopes that the Hong Kong authorities will exercise restraint and respect the protestors’ right to express their views peacefully.”

The Hong Kong demonstrations were triggered after the Chinese government restricted who can run as the commercial hub’s next chief executive, or leader.

Protestors have been angered by the central government’s refusal to allow free elections for the city’s next leader in 2017, insisting that only two or three candidates vetted by a pro-Beijing committee will be permitted to stand.

In Hong Kong, police equipped with riot helmets, gas masks and shields stood behind metal barricades as more than 3,000 protestors gathered outside the office of the embattled leader, Leung Chun-ying, early Thursday.

Wang threw Beijing’s support behind the Hong Kong authorities, saying they had the “capability to properly handle the current situation in accordance with the law.”

– Kerry-Wang talks –

In an unusual move, US officials revealed that the two men, who also have weighty regional and global issues on their agenda, were to meet for a second time at the State Department later Wednesday at the request of the Chinese delegation.

State Department spokeswoman Jen Psaki reaffirmed the US position.

“It’s clear that we want the people of Hong Kong to have a broad choice of candidates,” she said.

“We believe human rights and the freedom of expression is something that’s important not just in China but countries around the world,” she insisted, asked about Wang’s assertion that Hong Kong was an internal Chinese matter.

“We’re continuing to urge dialogue between the authorities and protestors,” she added.